Sneaking LSD into someone's beverage
Back in the day, I remember all those clowns who used to talk about doing this. I guess this movie is one source that gave them the idea. It's kind of like "I Love You, Alice B. Toklas" (which came out a year before "The Big Cube") giving people the idea to spike brownies with marijuana, then serve them to unsuspecting folks.
Man, people were reckless back in the druggie days!